Polymorphism is the phenotypic variation within a population. Polymorphism could spread locally through drift, selection, and gene flow. The land snail Cepaea nemoralis are most commonly found in two different coloured shell variations: banded light-coloured and dark unbanded. The banded light-coloured live in low vegetation- in grassfields and hedgerows whilst the dark unbanded live in the dark woodlands. Within this habitat there are multiple sub-habitats where the two variations can interact and produce polymorphs and there is a spectrum of shell colours and patterns within the polymorphs; light unbanded, dark banded, etc.
In order to determine how polymorphism in Cepaea nemoralis is affected by variations in habitat, we will use a stratified sampling method to reproduce the sub-populations. The samples will each be taken at three different heights; two samples per sub-habitat.
Hypothesis
Null hypothesis: There is no relationship between different habitat variations and shell colours and patterns in Cepaea nemoralis
Alternative hypothesis: There is a relationship between different habitat variations and shell colours and patterns in Cepaea nemoralis
Sampling Method
Materials:
A 10 x 10 quadrat
Gloves for hygiene and safety purpose
Note taking equipment
Field Methodology:
Place 10 x 10 quadrats at the sampling sites marked on the map below
Record number of snails found, and place into phenotype categories accordingly
Dead snails should also be recorded as they have biological significance
Sampling plan:
Second Draft
Introduction
Polymorphism isthe phenotypic variation within a population. It could spread locally through genetic drift, selection, and gene flow. Polymorphism provides the raw material for evolution, and in turn, evolutionary processes can help maintain polymorphism. The grove snailCepaea nemoralis are highly polymorphic; they can be found having either yellow, pink, or brown shell colour with zero to five bands. One of the forces which may cause polymorphism is visual selection, in which a predator e.g. a thrush, may prey on a certain phenotype more thus selection favours the other (Jones et al., 1977). This type of selection is important to consider in this experiment as it is expected that different types of shells will be found in different habitats and this could be due to camouflage against predators. Another type of selection which may affect the distribution of genes within this population is climatic selection. Due to different colours of shells, some individuals may absorb more thermal energy than others. This can affect distribution as dark coloured Cepaea will absorb more heat than the light coloured Cepaea and this could be a disadvantage thus may be selected against. Disruptive selection and gene flow may also influence polymorphism (Jones et al., 1977). The C. nemoralis species is slow moving (approximately 20 metres per generation) but it has been noted that populations do move between each other and this can lead to gene flow, although very limited, and increase the number of abnormal alleles within a population which can lead to polymorphism. All these processes can also occur alongside genetic drift, which is always acting upon the genetic makeup of the species in question. Apart from its distinctive shell colour variation, C. nemoralis are the ideal species for this study as their genotype can be easily identified from their phenotype and can be found locally in Pulpitt Wood, Buckinghamshire. This study aims to explain the difference in phenotypic variation in between 3 different habitats in Pulpitt Wood—grassland, woodland, and bushy habitat. We will study different habitats as it will enable us to determine whether the polymorphism seen within this species is the result of either natural selection or genetic drift. If natural selection is indeed occurring then we should see differences in phenotypes between each habitat. If it were just genetic drift, then there would be no significant relationships seen for each habitat and the polymorphisms seen will be randomly distributed.
Hypothesis
Null hypothesis: There is no significant difference in phenotypic variation between habitats since no selection is not acting upon polymorphism
Alternative hypothesis: There is a significant difference in phenotypic variation between habitats, so selection must be actin upon polymorphism
Methods
Using two transects allows us to sample twice form each sub-habitat, which reduces the impact of anomalies. Different colours will have different advantages depending on location. The selective pressures will change depending on the habitat; brown shells will be advantageous in the woodland habitat, whilst yellow shelled snails will have an advantage in grassy areas. So these two transects will allow us to identify the transition from brown shelled snails in the woodland habitat through the shrub habitat to the grass habitat where we will find the majority of yellow shelled snails.
Materials:
Gloves for hygiene and safety purpose
Note taking equipment
Field Methodology:
Collect 15 snails from each habitat
Record number of snails found, and place into phenotype categories accordingly
Dead snails should also be recorded as they have biological significance
Sampling plan:
Final Draft
Introduction
Polymorphism is the phenotypic variation within a population. It could spread locally through genetic drift, selection, and gene flow. Polymorphism provides the raw material for evolution, and in turn, evolutionary processes can help maintain polymorphism. The grove snail Cepaea nemoralis are highly polymorphic; they can be found having either yellow, pink, or brown shell colour with zero to five bands. One of the forces which may cause polymorphism is visual selection, in which a predator e.g. a thrush, may prey on a certain phenotype more thus selection favours the other (Jones et al., 1977). This type of selection is important to consider in this experiment as it is expected that different types of shells will be found in different habitats and this could be due to camouflage against predators. Another type of selection which may affect the distribution of genes within this population is climatic selection. Due to different colours of shells, some individuals may absorb more thermal energy than others. This can affect distribution as dark coloured Cepaea will absorb more heat than the light coloured Cepaea and this could be a disadvantage thus may be selected against. Disruptive selection and gene flow may also influence polymorphism (Jones et al., 1977). The C. nemoralis species is slow moving (approximately 20 metres per generation) but it has been noted that populations do move between each other and this can lead to gene flow, although very limited, and increase the number of abnormal alleles within a population which can lead to polymorphism. All these processes can also occur alongside genetic drift, which is always acting upon the genetic makeup of the species in question. Apart from its distinctive shell colour variation, C. nemoralis are the ideal species for this study as their genotype can be easily identified from their phenotype and can be found locally in Pulpitt Wood, Buckinghamshire. This study aims to determine the relative importance of different evolutionary processes between three different habitats in Pulpitt Wood—grassland, woodland, and bushy habitat. If naturalselection is stronger, we should see differences in the relative frequencies of phenotypes between each habitat. If genetic drift is stronger, then there would be no difference in the relative frequencies of phenotypes between each habitat.
Methods
Materials:
Gloves for hygiene and safety purpose
Note taking equipment
Field methodology:
Collect 15 snails from each habitat
Record number of snails found, and place into phenotype categories accordingly
Group Members
Kanahaya Alam (Secretary)
Sam Baker
Reshana De Silva
Liam Mackenzie-Mason
Jack Melaugh-McAteer
First Draft
Introduction
Polymorphism is the phenotypic variation within a population. Polymorphism could spread locally through drift, selection, and gene flow. The land snail Cepaea nemoralis are most commonly found in two different coloured shell variations: banded light-coloured and dark unbanded. The banded light-coloured live in low vegetation- in grassfields and hedgerows whilst the dark unbanded live in the dark woodlands. Within this habitat there are multiple sub-habitats where the two variations can interact and produce polymorphs and there is a spectrum of shell colours and patterns within the polymorphs; light unbanded, dark banded, etc.
In order to determine how polymorphism in Cepaea nemoralis is affected by variations in habitat, we will use a stratified sampling method to reproduce the sub-populations. The samples will each be taken at three different heights; two samples per sub-habitat.
Hypothesis
Null hypothesis: There is no relationship between different habitat variations and shell colours and patterns in Cepaea nemoralis
Alternative hypothesis: There is a relationship between different habitat variations and shell colours and patterns in Cepaea nemoralis
Sampling Method
Materials:A 10 x 10 quadrat
Gloves for hygiene and safety purpose
Note taking equipment
Field Methodology:Place 10 x 10 quadrats at the sampling sites marked on the map below
Record number of snails found, and place into phenotype categories accordingly
Dead snails should also be recorded as they have biological significance
Sampling plan:
Second Draft
Introduction
Polymorphism is the phenotypic variation within a population. It could spread locally through genetic drift, selection, and gene flow. Polymorphism provides the raw material for evolution, and in turn, evolutionary processes can help maintain polymorphism. The grove snail Cepaea nemoralis are highly polymorphic; they can be found having either yellow, pink, or brown shell colour with zero to five bands. One of the forces which may cause polymorphism is visual selection, in which a predator e.g. a thrush, may prey on a certain phenotype more thus selection favours the other (Jones et al., 1977). This type of selection is important to consider in this experiment as it is expected that different types of shells will be found in different habitats and this could be due to camouflage against predators. Another type of selection which may affect the distribution of genes within this population is climatic selection. Due to different colours of shells, some individuals may absorb more thermal energy than others. This can affect distribution as dark coloured Cepaea will absorb more heat than the light coloured Cepaea and this could be a disadvantage thus may be selected against. Disruptive selection and gene flow may also influence polymorphism (Jones et al., 1977). The C. nemoralis species is slow moving (approximately 20 metres per generation) but it has been noted that populations do move between each other and this can lead to gene flow, although very limited, and increase the number of abnormal alleles within a population which can lead to polymorphism. All these processes can also occur alongside genetic drift, which is always acting upon the genetic makeup of the species in question. Apart from its distinctive shell colour variation, C. nemoralis are the ideal species for this study as their genotype can be easily identified from their phenotype and can be found locally in Pulpitt Wood, Buckinghamshire. This study aims to explain the difference in phenotypic variation in between 3 different habitats in Pulpitt Wood—grassland, woodland, and bushy habitat. We will study different habitats as it will enable us to determine whether the polymorphism seen within this species is the result of either natural selection or genetic drift. If natural selection is indeed occurring then we should see differences in phenotypes between each habitat. If it were just genetic drift, then there would be no significant relationships seen for each habitat and the polymorphisms seen will be randomly distributed.
Hypothesis
Null hypothesis: There is no significant difference in phenotypic variation between habitats since no selection is not acting upon polymorphism
Alternative hypothesis: There is a significant difference in phenotypic variation between habitats, so selection must be actin upon polymorphism
Methods
Using two transects allows us to sample twice form each sub-habitat, which reduces the impact of anomalies. Different colours will have different advantages depending on location. The selective pressures will change depending on the habitat; brown shells will be advantageous in the woodland habitat, whilst yellow shelled snails will have an advantage in grassy areas. So these two transects will allow us to identify the transition from brown shelled snails in the woodland habitat through the shrub habitat to the grass habitat where we will find the majority of yellow shelled snails.Materials:
Gloves for hygiene and safety purpose
Note taking equipment
Field Methodology:
Record number of snails found, and place into phenotype categories accordingly
Dead snails should also be recorded as they have biological significance
Sampling plan:
Final Draft
Introduction
Polymorphism is the phenotypic variation within a population. It could spread locally through genetic drift, selection, and gene flow. Polymorphism provides the raw material for evolution, and in turn, evolutionary processes can help maintain polymorphism. The grove snail Cepaea nemoralis are highly polymorphic; they can be found having either yellow, pink, or brown shell colour with zero to five bands. One of the forces which may cause polymorphism is visual selection, in which a predator e.g. a thrush, may prey on a certain phenotype more thus selection favours the other (Jones et al., 1977). This type of selection is important to consider in this experiment as it is expected that different types of shells will be found in different habitats and this could be due to camouflage against predators. Another type of selection which may affect the distribution of genes within this population is climatic selection. Due to different colours of shells, some individuals may absorb more thermal energy than others. This can affect distribution as dark coloured Cepaea will absorb more heat than the light coloured Cepaea and this could be a disadvantage thus may be selected against. Disruptive selection and gene flow may also influence polymorphism (Jones et al., 1977). The C. nemoralis species is slow moving (approximately 20 metres per generation) but it has been noted that populations do move between each other and this can lead to gene flow, although very limited, and increase the number of abnormal alleles within a population which can lead to polymorphism. All these processes can also occur alongside genetic drift, which is always acting upon the genetic makeup of the species in question. Apart from its distinctive shell colour variation, C. nemoralis are the ideal species for this study as their genotype can be easily identified from their phenotype and can be found locally in Pulpitt Wood, Buckinghamshire. This study aims to determine the relative importance of different evolutionary processes between three different habitats in Pulpitt Wood—grassland, woodland, and bushy habitat. If naturalselection is stronger, we should see differences in the relative frequencies of phenotypes between each habitat. If genetic drift is stronger, then there would be no difference in the relative frequencies of phenotypes between each habitat.
Methods
Materials:
Gloves for hygiene and safety purpose
Note taking equipment
Field methodology:
Record number of snails found, and place into phenotype categories accordingly
Dead snails should also be recorded
Sampling plan
Legend: